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Chapter 7
2-6s
400ms
reward cue
task cue (600ms)
target
feedback
(600ms)
response
word
15 cent
TRIAL 4
high reward
task switch
response switch
le
le
right
correct!
15 cent
incorrect!
0 cent
TRIAL 3
low reward
task repeat
response switch
arrow
le
1 cent
le
right
correct!
1 cent
incorrect!
0 cent
TRIAL 2
low reward
task switch
response repeat
1 cent
arrow
right
le
right
correct!
1 cent
incorrect!
0 cent
TRIAL 1
15 cent
word
le
correct!
15 cent
le
incorrect!
0 cent
right
Figure 7.3
Task and response switching paradigm with reward manipulation
Participants had to respond to response-incongruent arrow-word combinations (targets) with a left
or right button press, either by responding to the direction indicated by the arrow (i.e. <- or ->) or to
the direction indicated by the word (i.e. ‘left’ or ‘right’). A task cue preceding the target (by 400ms)
indicated which task (arrow or word) the participant had to respond to on the current trial. Which task
was performed on a particular trial could either change unpredictably with respect to the preceding
trial (i.e. task switch trial; e.g. arrow – word as in trial 4, or word - arrow as in trial 2) or remain the
same (i.e. task repeat trial; arrow-arrow (trial 3), or word-word). In addition to such task switches, the
paradigm allowed us to look at response switches, i.e. whether the correct response (left or right button),
remained the same compared with the previous trial, or switched. In the current version of the paradigm
we made sure that the task switches occurred independently from response switches; half of the task-
switch trials and half of the task-repeat trials required a switch of the response button (e.g. trial 4 and 3
respectively, whereas the other half of the trials required a response repetition (e.g. trial 2). In addition
we manipulated the amount of anticipated reward (€0.01 vs. €0.15) on a trial-by-trial basis by means of
a reward anticipation cue. At the start of each trial this reward cue indicated the amount of reward on
that trial, contingent on a correct and sufficiently fast button press. Immediately following the response,
feedback was given (e.g., “correct! 15 cents”) (see also Aarts et al., 2015). The inter-trial-interval varied
(jitter of 2 – 6 seconds).
Paradigm
Participants performed a task-switching paradigm with a reward manipulation that has been
extensively described elsewhere (Aarts et al., 2015), with minor changes to include a response-
switching component. Details of the task are described in the legend of (
figure 7.3, box 2.3
).
At the start of each session, participants practiced the task (
figure 7.3
). The first practice block
(24 trials), which was only administered during the intake session, was merely a switching
task. During this block the task (i.e. whether to respond to the arrow or the word) alternated
unpredictably from trial to trial (
figure 7.3
) without any reward cues, and the feedback on